We have enrolled 24 patients to date. Two patients were excluded after enrollment secondary to unknown diagnosis at the time of enrollment of congenital heart disease. Preliminary biostatistical analysis after 10 patients determined that we will need to enroll 10 patients in each group (neonatal non-CDH, neonatal CDH, and pediatric) to achieve statistical significance in this study. There have been no adverse side effects from the study to date. The preliminary data of this pilot study is helping in the design of a clinical trial with C1 inhibitor concentrate for attenuating capillary leak in ECMO patients and decreasing time on ECMO. Data from our study was presented at the 1998 Annual Meeting of the Extracorporeal Life Support Organization in San Antonio and was accepted to be presented at the 1999 Society for Pediatric Research Meeting in San Francisco.